Thread breaking means for sewing machines



Oct. 20, 1953 N. KNAUS ET AL 2,655,887

THREAD BREAKING MEANS FOR SEWING MACHINES Filed July 15, 1950 2 Sheets-Sheet l rhvenfaa Nicholaus Knaus and Agnes Gilillinyfon Oct. 20, 1953 N. KNAUS ET AL 2,655,887

THREAD BREAKING MEANS FOR SEWING MACHINES Filed July 15, 1950 2 Sheets-Sheet 2 H ii- Ji z'venfazd vickolaus Knaus and A as Gillilli fan Wfne/MD "I9 Patented Oct. 20, 1953 THREAD BREAKING MEANS FOR SEWING MACHINES Nichclaus Knaus, Cranford, and Agnes G. Millington, Clifton, N. J., assignors to TheSinger Manufacturing Company, Elizabeth, N. J., a corporation of New Jersey Application July 13, 1950, Serial No. 173,537

This invention relates to thread breakers for sewing machines and more particularly to thread breakers for overedge sewing machines which chain off between successive articles, whereby the successive articles are connected together by an elastic thread-chain comprising concatenated loops of two or more sewing threads.

The invention has as its primary object to provide a thread breaker which will facilitate the manual severing of the thread chain, and which will prevent the pulling of the thread-chain off the chaining-off finger on the throat-plate and/or the presser-foot and the distortion of the thread loops thereof.

A further object of the present invention is to provide a thread breaker which will prevent the breaking of the needle as the thread-chain is moved laterally of the direction of work feed in order to sever the chain.

These and other objects have been attained by the provision of specially designed presser-foot, throat-plate and feed-dog elements which cooperate to snub and clamp the thread-chain so as to prevent the latter from being pulled off the chaining-off finger whenever the thread-chain is manually pulled laterally of the direction of feed for the purpose of breaking the chain.

With the above and other objects in view, as will hereinafter appear, the invention comprises the devices, combinations, and arrangements of parts hereinafter set forth and illustrated in the accompanying drawings of a preferred embodiment of the invention, from which the several features of the invention and the advantages attained thereby will be readily understood by those skilled in the art.

Fig. 1 represents an end elevation, partly in section, of an overedge sewing machine having elements embodying the present invention.

Fig. 2 represents a top plan view of a throatplate and feed-dog employed in the present sewing machine.

Fig. 3 represents a perspective view of dog employed in the present machine.

Fig. 4 represents a top plan view, partly in section, of a presser-foot together with portions of the sewing machine which cooperate therewith during the sewing operation, and a sewed article connected with the stitch-forming mechanism by the usual thread-chain.

Fig. 5 represents a fragmentary plan view similar to Fig. 4 but showing the sewed article as moved laterally sufficiently to sever the threadchain.

the feed- 6 Claims. (01. 112- 253) Fig. 7 represents a right-hand side view, partly in section, of the presser mechanism employed in the present machine.

Fig. 8 represents a bottom plan view of that portion of the presser mechanism disclosed in Fig. '7.

Referring more specifically to the drawings, the

sewing machine comprising a frame it, worksupporting plate ll, throat-plate l2, work-feeding mechanism comprising a feed-dog i3, a

i presser-foot l4 supported upon a presser-bar l5 and overlying the feed-dog l3 and maintaining the work in contact therewith, and stitch-forming mechanism including a reciprocating curved eye-pointed needle l6, and a cooperating loopspreader ll. Inasmuch as most all of the abovementioned elements are common to overedge sewing machines and form no part of the present invention, detailed illustration and description of each of such elements is deemed unnecessary.

Secured to the throat-plate l2, and forming a part thereof, is a chaining-off finger I8 common to overedge sewing machines, which underlies the edge of the work-piece and about which stitches f are formed. If desired, a chaining-off finger l9 may also be carried upon the presser-foot id in a manner such that it will cooperate with the chaining ofi finger l 8 carried by the throat-plate. As is customary, the chaining-off fingers i8 and 19 have free and unsupported'rear ends which i permit the stitches formed thereabout to be fed reference numeral 20.

therefrom in the form of an elastic thread-chain. This chain is indicated in the drawings by the In Fig. 4, an article 2! is shown as having passed beyond the stitching mechanism and as having one edge thereof covered by overedge stitches. ,After passage of the article, the machine chains ofi, thereby producing the chain until the succeeding article is presented to the stitch-forming mechanism. It is this connecting chain between these successive articles that is required to be severed.

The presser mechanism of the present device I comprises a substantially horizontally disposed Z tional manner.

Fig. 6 represents a sectional view takensubv stantially along the line 6-6 of Fig. 4:.

' presser-bar K5, the rear end portion of which is mounted upon a universal joint 23 in the conven- This presser-bar I5 is substantially L-shaped and the shorter limb 24 thereof depends from the longer limb 25 and has pivotally secured upon its free end portion the presser-foot 14. The basic details of the present presser mechanism is disclosed in .a U. S. patent of Knaus No. 2,419,494, April 22, 1947.

As is best disclosed in Figs. 1, 4', 7 and 8, the present presser-foot l4 comprises a sole-plate 26 having an upturned toe portion 2! at its forward end, and projecting outwardly from one longitudinal edge of the presser-foot is the usual chaining 01f finger I 9. The present foot, however, differs from its usual prior counterpart in that its rearward portion is provided with an upturned heel .28 which is formed with an elongated aperture 29 adapted to receive the lower end portion of a thread-deflecting finger 30; the upper end portion of which is secured to the presser-bar 15 by means of a screw:3| It will be observed that the presser-foot aperture 29 is sufficiently large to permit relative pivotal .movements between the presser-bar l5 and 'the foot 114 without interference from the thread-deflecting finger 30. The present foot also differs from its prior counterpart in that it is provided with a thread-guiding shoulder or incline 32 which is formed at the junction of the longitudinal edge portion 33 and the upturned heel member 28. The function of the .heel member 28, together with its thread-guiding bevel 32 and the thread deflecting finger 30, will be described hereinafter.

The above noted throat-plate I2 is adapted to be secured to the sewing machine frame it by means of screws 34, 3 3 and the basic details of this throat-plate are disclosed in the United States patent of Knaus No. 2,238,796, April 15, 1941. The present throat-plate, however, differs from its prior counterpart disclosed in the above noted Knaus patent in that it has its rear edge portion beveled as at 35, at a location substantially beneath the presser-foot bevel. 32 so as to form with the presser-foot bevel a guide-throat which will direct the thread chain 29 between the 1 throat-plate and the vpresser-foot whenever thread-chain is pulled laterally of the direction of work feed.

Referring particularly to Fig. 6, it will. be ob-- served that the throat-plate chaining-off finger I8 is disposed directly beneath the chaining-off finger ii! of the presser-ffootand these two fingers cooperate together in the conventional manner .for forming the overedge stitches.

Referring particularly to Figs. 1, 2 and 3, the present sewing machine is provided with a feeddog I3 which is secured to the feed-bar 22 by means of a screw 35 in a conventional manner. Fora more complete disclosure and description of a feed mechanism of this type, reference may be had to the prior U. S. patent of Knaus No. 2,238,796, April 15, 1941. The present feed-dog, however, differs from its prior counterpart in that it is formed with a row of teeth, the crowns 31 of which define a singl horizontal plane. Referring particularly to Figs. 1 and 3, it will be seen that the teeth 38, formed on a rearward portion of the feed-dog, are substantially shorter than the forward teeth 33. These shorter teeth 38 are provided so that when the thread-chain is pulled over the rear portion ofthe feed-dog the rear teeth will be short enough so as to permit the thread-chain .to be properly clampedbetween the feed-dog and the presser-foot to the end that the thread-chain can be broken without defiecting the needle or pulling the thread-chain off the chaining-on fingers.

The operation inbreaking the threadchain is as follows: one article 2| having had its edge covered with overedge stitches and the machine having continued to sew, thereby producing the thread-chain '20, as illustrated in Fig. l, the openator grasps the article and moves it laterally to the position indicated in Fig. 5. This movement of the article carries the thread-chain diagonally beneath the presser-foot and into the throat 4 formed by the bevel 35 of the throat-plate and the bevel 32 of the presser-foot so that the chain will be carried between the presser-foot and throat-plate to the end that it will be caught and clamped therebetween. Further movement of the article or the thread-chain in this lateral direction will, of course, sever the same. It will be understood that the clamping action between the presser-foot and throat-plate will be sufiicient to sever the chain and at the same time this clamping action will prevent the thread-chain from being pulled off the chaining-off fingers or being pulled sufiiciently hard to deflect or break theneedle. Since it is possible for the threadchain to be pulled over the rear portion of the feed-dog during the thread-chain breaking operation, the rear half of the present feed-dog, as hereinabove noted, is formed with teeth 38 which are substantially shorter than the forward teeth 39. Thus, even through the thread chain 29 is pulled over the rear portion of the feed-dog, the rear teeth are short enough so as to permit the thread-chain to be clamped properly between the feed-dog and the presser-foot to the end that the thread-chain can be broken without deflecting the needle or pulling the thread-chain off the chaining-off fingers.

The thread-deflecting finger 39, being positioned between the heel .portion'EB of the presserfoot l4 and the free endiportion of the presserb'ar l5, will prevent the operator from inadvertently pulling the thread-chain across the upper portion of the presser-foot, and thus the thread-chain 24] will always be properly inserted between the presser-foot and the throat-plate in a manner as "hereinabove described. Further more, since the lower portion of the threaddefiecting finger 30 is received within the elongated aperture 29 of the presser-ioot, the latter element will .be permitted to pivot about the free end portion 24 0f the presser-bar 15 in a conventional fashion. However, the thread-deflecting finger 3B and the presser-foot it ar so associated that there is no opportunity'for the thread-chain 20 to be caught on either of these two elements when the chain is pulled laterally of the feed direction for the purpose of breaking the same.

Referring particularly to Fig. 6, it will be observed that there is illustrated in this figure the manner in which the thread-chain 28 may be caught between the short rearward teeth 38 of the feed-dog and the sole-plate 25 of the presserfoot, so that the thread-chain may be properly clamped even through the feed-dog is in its raised position. Clamped in this position, the thread will break at a point beneath the presser foot whenever the operator pulls upon the chain in a lateral direction.

From the abov'eyit will be appreciated that the present specially designed presser-foot, throatplate and feed-dog elements operat in concert to snub and clamp the thread-chain soas to prevent the latter from being pulled oi? the chainingoff fingers whenever the thread-chain is manually pulled laterally of the direction of feed for the purpose of breaking the same. Furthermore, experience has indicated that the pressure between the ,presser-foot and the throat-plate or between the presser-footand the feed-clog is sub ficient at all times to effect the breaking of the thread-chain whenever the latter is pulled laterally in a manner as above described.

Having thus set forth the nature of the invention, what we claim herein is:

1. A work-pressing mechanism for use with a chain-stitch sewing machine, comprising asubstantially L-shaped presser-bar, a presser-foot including an elongated sole-plate pivotally carried upon the free end portion of the shorter limb of said presser-bar with the sole-plate normally disposed in parallelism with the longer limb of said presser-bar, said presser-foot havingan upturned forward toe and an upturned rearward heel, and a thread-deflecting guard finger extending upwardly between the rear face of said heel and one limb of said presser-bar.

2. A work-pressing mechanism for use with a chain-stitch sewing machine, comprising a substantially L-shaped presser-bar, a presser-foot including an elongated sole-plate pivotally carried upon the free end portion of the shorter limb of said presser-bar with the sole-plate normally disposed in parallelism with the longer limb of the presser-bar, said presser-foot having an upturned forward toe and an upturned rearward heel, and a thread-deflecting guard finger having one end portion thereof secured upon the longer limb of said presser-bar and the other end thereof being associated with the rear face of the upturned rearward heel of said presser-foot.

3. A work-pressing mechanism for use with a chain-stitch sewing machine, comprising a substantially L-shaped presser-bar, a presser-foot including an elongated sole-plate pivotally carried upon the free end portion of the shorter limb of said presser-bar with the sole-plate normally disposed in parallelism with the longer limb of said presser-bar, said presser-foot having an upturned forward toe and an upturned rearward heel, said upturned rearward heel having a horizontal slot formed therein, and a thread-deflecting guard finger having one end portion thereof secured upon one limb of said presser-bar and the other end thereof extending downwardly to a position adjacent the rear face of said upturned heel and being received within the slot formed in said upturned heel so that the free end of such limb will be disposed adjacent the forward face of said upturned heel.

4. In a sewing machine, a work-support, a presser-bar, stitch-formin mechanism including a reciprocatory thread-carrying needle and an oscillatory thread-carrying member cooperating with said needle in the formation of enchained stitches, a work-advancing feed-dog operating through said work-support, the upper portion of said feed-dog being provided with a row of teeth, a presser-foot carried by said presser-bar and being opposed to said feed-dog and having an upturned forward toe and an upturned rearward heel, an upwardly inclined thread-guiding shoulder provided on the lower sole portion of the presser-foot at the junction of one longitudinal edge portion of said presser-foot and said upturned heel to facilitate the bringing of the thread laterally of the direction of work-feed and between the feed-dog teeth and the sole portion of said presser-foot and a thread-deflecting guard having its upper end carried by said presser-bar and with its lower end extending downwardly to a position adjacent the rear face of said upturned heel.

5. In a chain-stitch sewing machine, stitchforming mechanism including a reciprocatory thread-carrying needle, a work-support in the form of an apertured throat-plate having its upper surface adjacent its rear edge portion provided with a downwardly and rearwardly beveled corner, a work-advancing feed-dog operating through said throat-plate, and a presser-foot opposed to said feed-dog and including an elongated sole-plate having one longitudinal edge portion thereof disposed adjacent the path of needle reciprocation, the entire rear portion of said presser-foot being inclined upwardly and the corner portion of said presser-foot sole-plate adjacent said longitudinal edge portion and said rear portion being beveled upwardly and disposed over the throat-plate corner thereby to facilitate the bringing of the sewing thread laterally of the direction of work-feed and between the throat-plate and the presser-foot.

6. In a chain-stitch sewing machine, stitchforming mechanism including a reciprocatory thread-carrying needle, a work-support in the form of an apertured throat-plate having its upper surface adjacent its rear edge portion provided with a downwardly and rearwardly beveled corner, a work-advancing feed-dog operating through said throat-plate, a substantially L- shaped presser-bar disposed with its longer limb substantially in parallelism with the upper surface of said throat-plate, an elongated presserfoot pivotally carried upon the free end portion of the shorter limb of said presser-bar, said presser-foot having an upturned forward toe and an upturned rearward heel and havingone longitudinal edge portion thereof disposed adjacent the path of needle reciprocation, said presserfoot being provided at the junction of its heel and said longitudinal edge with an upwardly inclined corner disposed over the throat-plate corner thereby to facilitate the bringing of the sewing thread laterally of the direction of work- I feed and between the throat-plate and the presser-foot, and a thread-deflecting guard finger disposed rearwardly of said presser-foot and extending between said heel and the longer limb of said presser-bar.

NICHOLAUS KNAUS. AGNES G. MILLINGTON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,602,140 Avis Oct. 5, 1926 2,074,655 Lindner Mar. 23, 1937 2,157,373 Weis May 9, 1939 2,184,604 Ray Dec. 26', 1939 2,366,113 Kessler Dec. 26, 1944 2,470,931 Jennings May 24, 1949 

